Row over family values splits Cabinet

A leading minister is to rally to the defence of single parents amid a growing cabinet split over whether the government should champion marriage. Alan Johnson, the Education Secretary, will warn that family policy should not be based on 'the prejudices of yesterday's generation' or hung up over whether parents are married or not, but focused on what children need.

His words will be seen as a sharp change of direction from the line championed by the Work and Pensions Secretary, John Hutton, backed by Number 10, arguing that two parents may be better than one for children and that the benefits system at present discriminates against marriage.

Johnson will tell a conference on Tuesday: 'Family policy must be bias-free - to express it in a more Clintonesque manner, "It's the parenting, stupid". Not all children from married couples fare well, and other family structures are not irretrievably doomed to fail.'

His intervention comes as figures close to Gordon Brown criticised Downing Street for not responding more quickly or coherently to David Cameron's promises of tax breaks for married couples or to his argument that absent fathers are to blame for gun and gang culture. The government had failed to show a lead and stand up for lone parents and cohabitees, said sources in the Chancellor's camp: 'It almost smacks of "well, maybe we should be looking at some of these things", but on what possible planet would we be looking at [tax breaks]?'

The issue is incendiary because it strikes at the heart of politicians' private lives. Tony Blair, famed for one of the strongest marriages in politics, is said to be concerned that the Conservative leader's argument has resonance, while other colleagues fear the demonisation of single parents and cohabitees. Brown's wife, Sarah, was raised by her mother for some years after her parents divorced and the couple are close to author J K Rowling, who has campaigned on behalf of lone parents.

Blair will try to get the parenting debate on an even keel this week, highlighting a review to be carried out by the social exclusion minister, Hilary Armstrong, on why some families fall through the net.

Johnson will also publish a parenting strategy soon, covering everything from pre-school childcare to teenage problems. He will tell the conference organised by Relate, the relationship counselling organisation: 'Strong relationships represent the key to successful parenting. And marriage represents the pinnacle of a strong relationship.' But he will add that tax breaks for marriage would be pointless: 'Taxation and law cannot create a family: it's commitment and love.'

However, there is alarm among ministers that the government has been slow to enter the rumbling debate. 'Frankly Cameron has been allowed to get far, far, too far with this family stuff,' said one senior minister sympathetic to Brown. 'He is entrenching a stereotype when loads of kids from one parent families are doing terribly well.'

Johnson will also tell the conference that while a recent report by Unicef, which controversially found Britain's children fared among the worst in Europe, had shone a light on family issues to claim that society was in deep trouble as a result, 'is not only gross hyperbole, it's also wholly inaccurate'.

Armstrong backed up the argument, saying 'collective moral despair' over recent tragic events was unnecessary. 'Our policies have not created a widespread culture of excluded youth, or an "asbo generation"'. A Cabinet Office source added that tax breaks 'to bribe couples to stay together' did not tackle the root causes of social exclusion.

Cameron went back on the offensive, telling Choice FM radio: 'We need to encourage a culture that says the family is the most important part of society, sticking together is really important, commitment is important and dads have responsibilities.'

Yesterday Harriet Harman, the minister for family policy, joined the attack, dismissing Cameron's arguments as 'Back to Basics in an open-necked shirt'.